The Icelandic cloud formations are just beautiful, so remember to look up at the endless skies while you are here on vacation. Great for world class cloud photographing. This photo is from Búðardalur, Iceland, by Ben Cowden.
Mammatus Clouds - "True to their ominous appearance, mammatus clouds are often harbingers of a coming storm or other extreme weather system. Typically composed primarily of ice, they can extend for hundreds of miles in each direction.